Moisture sensor for purging system

ABSTRACT

A moisture sensor detects the presence of foreign matter in a fluid conducting conduit and produces an electrical signal which activates a pump to purge the conduit of the foreign matter. The moisture sensor includes a pair of conduits that may be formed of an electrically conductive material and a coupling for placing the pair of conduits in fluid communication. A pair of electrodes are mounted in the coupling and are insulated from one another until electrically conductive foreign matter bridges a gap between the electrodes. Bridging the gap between the electrodes causes a signal to be sent to a source of gas that injects gas in the conduits to remove the foreign material therefrom.

This is a division of application Ser. No. 927,372, filed July 24, 1978,now U.S. Pat. No. 4,270,564.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to purging systems for fluid conductingconduits and more particularly to purging apparatus for removingmoisture from gas lines in respiratory monitoring systems.

2. Description of the Prior Art

In the field of respiration monitoring, it has been the general practiceto employ pump and vacuum equipment to remove mucous and moisture fromthe respiratory gas lines of the system introduced by coughing spasmsand edema of the patient so that the respiratory gasses may flow freelythrough the lines. Although such equipment has served the purpose, ithas not proved entirely satisfactory under all conditions of service forthe reasons that considerable difficulty has been experienced in sensingor detecting the presence of moisture and mucous in the lines anddifficulties encountered in minimizing the number of components and costof a purging system.

Those concerned with the development of purging systems for respiratorymonitoring apparatus have long recognized the need for a simple andreliable moisture sensor or detector coupled with a system of electricaland mechanical components which efficiently and economically purge therespiratory gas lines and remove drops of moisture and mucous. Thepresent invention fulfills this need.

One of the most critical problems confronting designers of respiratorymonitoring purging systems has been the design of a reliable and lowcost moisture sensor or detector. This problem is overcome by thepresent invention.

SUMMARY OF THE INVENTION

The general purpose of this invention is to provide a purging ormoisture removal system which embraces all the advantages of similarlyemployed purging apparatus and equipment and possesses none of theafore-described disadvantages. To attain this, the present inventioncontemplates a simple low cost and reliable moisture sensor incombination with an electrical counter and timer circuit wherebyunreliable detection of moisture and the undetected clogging ofrespiratory monitoring gas lines are avoided.

An object of the present invention is the provision of a gas conduitpurging system which is activated by a simple and reliable conductivitymoisture sensor.

Another object is to provide a purging system for gas lines in arespiratory monitoring system which is activated periodically to removemoisture and mucous.

A further object of the invention is the provision of a purging systemwhich is activated by the presence of moisture to purge respiratorymonitoring system gas lines of moisture and mucous over an adjustableduration of time.

Still another object is to provide a respiratory gas line purging systemwhich is periodically activated to remove moisture and mucous inaddition to being activated upon the detected presence of moisture andmucous.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings in which like referencenumerals designate like parts throughout the figures thereof andwherein;

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a block diagram of the elements comprising a preferredembodiment of the invention;

FIG. 2 illustrates a partial diagrammatic, circuit and block diagram ofsome of the elements of FIG. 1;

FIG. 3 illustrates a diagrammatic view of the moisture sensor of FIG. 1;

FIG. 4 illustrates a cross-section of the sensor of FIG. 3 taken alongline 4--4 of FIG. 3 in the direction of the arrows;

FIG. 5 shows a block diagram of the components comprising an alternateembodiment of the invention with the sensor at the imput to the systemand with two pumps;

FIG. 6 illustrates a block diagram of the components of anotherembodiment of the invention with the sensor at the input to the systemand a single pump;

FIG. 7 shows a perspective view of an alternate disposable sensor with aconnecting chamber;

FIG. 8 is a cross-section of the sensor of FIG. 7 taken on the line 8--8in the direction of the arrows; and

FIG. 9 is a block diagram of the components of a system using the sensorof FIGS. 7 and 8.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the drawings wherein like reference charactersdesignate like or corresponding parts throughout the several views,there is shown in FIG. 1 (which illustrates a preferred embodiment) afluid conduit or input gas line 11 which is adapted to be connected to asource of gas or fluid such as a respiratory system for analysis ofrespiratory gasses. Conduit 11 in turn is connected to a fluid or gasline connector 13 which connects conduit 11 to fluid or gas lineconduits 15 and 17. Conduit 15 is connected to a moisture or foreignmaterial sensor 19 having a pair of electrodes 21 and 23 extendingtherefrom and which is further connected by a conduit 25 to a gas orfluid analyzer 27. Analyzer 27 is further connected by a conduit 29 to aflow meter 31 which, in turn, is connected by a conduit 33 to aconnector 35. Connector 35 connects conduit 33 to a conduit 37 and aconduit 39, conduit 37 being in turn connected to an adjustable orthrottle valve 41, which is connected to a vent conduit 43. Conduit 39is connected to a 3-way solenoid valve 45 which is activated by asolenoid 47. 3-way solenoid valve 45 normally connects conduit 39 with aconduit 49 and upon operation of solenoid 47, connects conduit 49 with aconduit 51. Conduit 49 is further connected to a pump 53 which in turnis connected to a conduit 55. Conduit 51 is further connected to theoutput conduit or tube of a sump container 57 which in turn has an inputtube connected to conduit 17.

Electrode 21 of sensor 19 is connected to a common ground and electrode23 of sensor 19 is connected to one of two inputs to an electrical gate59. The other input of gate 59 is connected to a purge period selectswitch 61 which in turn is connected to an electrical counter 63 throughany one of a plurality of counter output terminals 65a through 65f.Counter 63 is further connected to a clock 67 which provides a source ofelectrical pulses to be counted by counter 63.

The output of gate 59 is further connected to an electrical timer 69having a variable resistance 71 for adjusting purge duration. Timer 69is further connected to an amplifier or driver 73 which in turn isconnected to solenoid 47 to actuate solenoid 47.

It should be noted that analyzer 27 may be any one of a well knownvariety of gas analyzers utilized for the analysis of respiratorygasses, and that flow meter 31 may be one of the well known flow metervarieties used to monitor the flow of respiratory gasses. Pump 53 may beof the well known rotating vane or blade type as well as a reciprocatingpiston type pump or one of the other types of well known vacuum pumpsutilized to move gaseous components through a system of conduits and gasdevices. Pump 53 may also be the vacuum system of a hospital instead ofa specific pump device. Sump 57 may be a container of the type wellknown in the gas analysis field for the trapping and collecting ofmoisture and foreign matter. Clock 67 may be any stable source ofalternating voltage or current well known in the field of electronicsand counter 63 may be a conventional electronic counter circuit whichproduces periodic signals of different frequency at each of itsplurality of output terminals such as RCA CD-4020. Gate 59 may be aconventional semi-conductor "AND" gate such as National Semiconductor 74CO8 and timer 69 may be a well known electronic timing circuit such as amono-stable flip-flop with adjustable duration or a Signetics 555.Amplifier 73 can be a conventional semi-conductor amplifier such as atransistor for driving the coil of solenoid 47.

Turning now to FIG. 2 there is illustrated diagrammatically a sensorhaving a pair of fluid or gas conduits 75 and 77 which are electricallyconductive and which are separated by an insulating conduit 76.Electrically conductive conduit 75 in turn is connected to conduit 15,and electrically conductive conduit 77 in turn is connected to conduit25. Electrode 23 which is connected to conduit 75 is further connectedto a common ground and electrode 21 which is connected to conduit 77 isconnected to a capacitor 83 which in turn is connected to electrode 23.Electrode 21 is further connected through a resistor 85 to a source ofpositive voltage +V through a terminal 87. Terminal 87 is furtherconnected through a resistor 89 to one side of a capacitor 91 which inturn is connected to switch 61 which in turn selects any one of thevarious outputs 65a-65c from counter 63 which in turn is activated by 60Hz clock 67.

One input to gate 59 is connected to the junction of capacitor 83 andresistor 85 and the other input to gate 59 is connected to the junctionof capacitor 91 and resistor 89. Timer 69 is connected to the output ofgate 59 and also is further connected to a source of voltage +V andfurther is connected to a variable resistor 71 and a capacitor 93 whichcapacitor also is connected to common ground along with one terminal oftimer 69. The output of timer 69 is further connected through a resistor95 to the base of a transistor 97 having the emitter thereof connectedto the common ground and the collector thereof is connected to solenoid47 of the 3-way solenoid valve.

FIG. 3 shows a diagrammatic view of sensor 19 illustrating an insulatingbody 79 housing and insulatively supporting in series and spacing apartelectrically conductive gas conduits 75 and 77 which are respectivelyconnected (not visible) to electrodes 23 and 21 extending at rightangles therefrom and protruding from body 79. Sensor 19 is made from lowcost materials and by economical fabrication methods so as to bedisposable for reasons hereinafter stated.

A more detailed cross section view of sensor 19 is illustrated in FIG.4. Insulating body 79 holds electrically conductive conduits 75 and 77separated by a hollow gap 81. Electrode 23 is imbedded in insulatingbody 79 and has a hole therethrough through which electricallyconductive conduit 75 passes and which is electrically connectedthereto. Similarly, electrode 21 is imbedded in insulating body 79 andhas a hole therethrough through which electrically conductive conduit 77and is electrically attached thereto.

In FIG. 5, sensor 19 is connected to an input conduit 97, which may be acatheter connected to a patient. A conduit 99 connects sensor 19 toconnector 13 which in turn connects conduit 99 to conduits 101 and 103.Conduit 103 is connected to analyzer 27 which in turn is connected byconduit 29 through flowmeter 31 to a conduit 105. Conduit 105 isconnected to vacuum pump 53. Conduit 86 is connected to a pressure pump107 which which in turn has an inlet conduit 109. Sensor 19 iselectrically connected to a control circuit 111 which in turn activatespump 107 when moisture is present in sensor 19 and activates pump 53when no moisture is present.

FIG. 6 illustrates substantially the same arrangement of componentsshown in FIG. 1 with adjustable valve 41 being removed and sensor 19being relocated in the input line. Conduit 97 is connected throughsensor 19 to conduit 99 which in turn is connected through connector 13to a conduit 103 and conduit 17. Conduit 103 is connected throughanalyzer 27, conduit 29 and flow-meter 31 to a conduit 113. Conduit 113in turn is connected to three-way solenoid valve 45 which normallyconnects conduit 113 to pump 53. Sensor 19 is electrically connected toa control circuit 115, which includes the electrical circuitry ofFIG. 1. Control circuit 115 is further connected to solenoid 47 ofthree-way solenoid valve 45.

It should be noted that in both FIGS. 5 and 6 Sensor 19 is required tobe disposable since moisture accumulated therein is pumped during purgein the reverse direction through the patient's catheter tube or conduit.Therefore, sensor 19 can only be used for one patient for this reason.

FIG. 7 is a perspective view of an alternate embodiment 113 of the fluidor moisture sensor illustrated in FIGS. 3 and 4. A supporting connectingmember 115, which may be a ribbed panel, is attached to insulatingconduit 76 and to a cylindrical enclosure 117 and holds conduit 76 in aspaced relationship to enclosure 117. Electrically conducting conduit 75is attached to one end of conduit 76 and electrically conducting conduit77 connects the other end of conduit 76 with enclosure 117. A pair ofcylindrical tubes or connecting ports 119 and 121 communicate with theinterior of enclosure 117. The body of sensor 113 maybe integrallymolded from plastic or other moldable low cost material and the like.After being used on a patient, sensor 113 may be discarded.

FIG. 8 is a cross-section of sensor 113 showing conducting conduits 75and 77 insulated by connecting conduit 76 and separated by gap 81.Conduit 77 joins connecting conduit 76 to a cylindrical chamber 127within enclosure 117. Connecting port 119 has an opening 123 whichconnects with chamber 127 and connecting port 21 has an opening 125which connects with chamber 127. A sealing plug 129 closes the end ofchamber 127 which end is open only for fabrication purposes. Panelmember 115 joins conduit 76 with enclosure 117.

FIG. 9 shows input conduit 109 connected to pressure pump 107 which inturn is connected by a conduit 131 to a 3-way solenoid valve 133 whichis actuated by a solenoid 135 to connect conduit 131 to a conduit 137.Conduit 131 is normally connected through solenoid valve 133 to aconduit 139 which in turn is connected through a pressure relief valve141 to an output conduit 143 which vents to outside air.

Conduit 131 is joined through actuated solenoid valve 133 to conduit 137which in turn is connected to port 121 of sensor 113. Port 119 of sensor113 is connected through a conduit 145 to a 3-way solenoid valve 149which is actuated by a solenoid 151. Solenoid valve 149 normallyconnects conduit 145 to a conduit 155 and when actuated connects conduit155 to a conduit 153. Conduit 153 is connected through a throttle oradjustable valve 157 to an input conduit 159 which may in turn beconnected to a source of reference or calibrating gas or to outside airas desired. Conduit 155 is connected through analyzer 27 to conduit 29which in turn is connected to flow meter 31 which in turn is connectedthrough conduit 105 to vacuum pump 53. Vacuum pump 53 is connected to anoutput conduit 163 which may vent to outside air.

Electrical conducting lines 167 and 169 are respectively connected toconductive conduit 77 and 75 and to a control circuit 165. Controlcircuit 165 is electrically connected to solenoid 151 by electrical line171 and to solenoid 135 by electrical line 173.

Control circuit 165 may contain the components as shown in FIG. 2 or useother electrical components well known to electrical designers tooperate electromagnetic valves from signals generated by electricalsensors.

Operation of the invention may be understood by first referring to FIG.4 wherein it can be seen that when a droplet of moisture or mucousbridges gap 81, electrically conductive conduit 75 is conductivelyconnected to electrically conductive conduit 77 establishing a lowresistance path between electrodes 21 and 23. Typical dimensions of gap81 are 0.041 inches in diameter and 0.045 inches in length.

Turning to FIG. 2 it can be seen that the low resistance path betweenelectrodes 21 and 23 is in parallel with capacitor 83 and causes a largevoltage drop across resistor 85 such that the voltage input to gate 59falls to a low potential voltage close to ground potential. This in turncauses the output of gate 59 to drop to a low potential voltage whichtriggers or fires timer 69. The output of timer 69 activates transistor97 which energizes solenoid 47 of 3-way solenoid valve 45 illustrated inFIG. 1.

The activation of 3-way solenoid valve 45 disconnects pump 53 fromconduit 39 and connects pump 53 to conduit 51. This causes moisture andmucous from conduits 11 and 15 to be forced through conduit 17 into sump57. During this time of purge duration, outside air enters through ventvalve 41 and flows through conduits 37 and 33 connected by connector 35,flow meter 31, conduit 29, analyzer 27, conduit 25 and sensor 19, in thedirections indicated by the arrows having a "rectangle" tail. Air flowsin this manner through conduit 15 and conduit 17 into sump 57 along withgasses entering through conduit 11 into sump 57. This causes themoisture and mucous detected by sensor 19 to be forced into the sump andcollected there along with other droplets of moisture and mucous thatmay have collected in other portions of the conduits and analyzer systemcomponents.

Turning to FIG. 2, resistor 71 of timer 69 sets the purge time durationwhich is typically adjusted to 15 seconds. Timer 69 will remainactivated as long as sensor 19 indicates moisture. However when thecondensation or moisture or mucous bridging gap 81 of sensor 19 isremoved, the timer will remain activated for the purge time duration toassure that other droplets of moisture or foreign material are removed.The purge period is determined by variable resistor 71 and capacitor 93in a typical well known RC time constant circuit.

Normal operation is illustrated in FIG. 1 by the direction of the arrowshaving a "circle" tail. Gas to be analyzed enters through conduit 11,connector 13, conduit 15, sensor 19, conduit 25, analyzer 27, conduit29, flow meter 31, conduit 33, connector 35, conduit 39, 3-way solenoidvalve 45, and through conduit 49 and pump 53 to output conduit 55.During this process, analyzer 27 quantitatively and qualitativelyanalyzes the gas mixture for the constituents that are desired to bedetected. However, in monitoring respiratory systems, there isencountered a high level of moisture from the breathing of the patientbeing monitored along with occasional globules of mucous and otherforeign material produced by coughing spasms and conditions of edema ofpatients. As this unwanted material accumulates in the conduits, itimpedes the flow of gas and disrupts the ability of the analyzer toperform its analytical function. Therefore, it is necessary from time totime to purge the system of this foreign material to enable the analyzerto indicate the quantity and quality of constituents of the respiratorygasses.

Although the moisture collected to gap 81 of sensor 19 is indicative ofthe moisture content of the conduits, it is possible for the gasconduits to collect moisture or mucous which block the flow of gasseswithout the sensor indicating the presence of this material by producinga low resistance path between electrodes 21 and 23. Therefore, clock 67and counter 63 provide for an automatic purge by setting switch 61 toany of a number of counter outputs which provide a variety of timeperiods between automatic purges. For example, by setting switch 61 tooutput terminal 65a, a low voltage output pulse occurring every fourminutes causes the input voltage of gate 59 to drop to activate timer 69every four minutes automatically whether or not sensor 19 detected thepresence of moisture or mucous. Therefore, every four minutes a purgewould occur lasting for a purge duration of, say, fifteen seconds. Bysetting switch 61 to terminal 65b of counter 63, a 15 second purge maybe obtained every two minutes. It should be noted that the timedurations of the purge periods and the number of selectable purgeperiods from the counter are the choice of the designer and user.

It should be remembered that gate 59 is designed to produce a low outputvoltage when either of its inputs are low or if they are both low.Therefore, if either the sensor or the counter or both produce a lowinput voltage to gate 59, timer 69 is activated to produce a purge ofthe system.

Operation of the arrangement of FIG. 5 involves two pumps 53 and 107.When no moisture is present the respiratory gasses being analyzed flowin the direction of the arrows with "circle" tails. Pump 53 is a vacuumpump which produces flow in this direction. When moisture is sensed insensor 19, control circuit 111 removes power from vacuum pump 53 andapplies power to pressure pump 107 which in turn pumps air in thedirection of the arrows with "rectangle" tails. Air flowing in responseto pump 107 forces the moisture out through activating sensor 19 andinlet conduit or catheter 96 in a reverse direction to the normal flowof respiratory gasses produced by pump 53.

It should be noted that in FIG. 5 two pumps are required and the sensormust be disposable as mentioned herein before. However, no sump isrequired since the unwanted moisture and mucous are pumped out of theinput conduit or catheter.

In FIG. 6 a sump is used as in FIG. 1 but sensor 19 is in the inputconduit or catheter as in FIG. 5. Furthermore, with the deletion ofvalve 41, there is no reverse flow of air through the analyzer duringpurge as is the condition of FIG. 1. As set forth in respect to FIG. 5,sensor 19 must be disposable because of its location in the inputcatheter.

Sensor 113 of FIGS. 7 and 8 operates in the same manner as sensor 19 ofFIGS. 3 and 4. Moisture or mucous bridging gap 81 lowers the electricalresistance between conduits 75 and 77. This productivity change may bedetected by a circuit similar to that illustrated in FIG. 2. However,sensor 13 has chamber 127, which is larger in diameter than conduits 75and 77, and acts as a miniature sump which traps any moisture and mucousthat may enter to prevent interference with and contamination of themeasuring equipment and tubing in the monitoring system. Normally apatient's catheter is connected to conduit 75 and samples of thepatient's respiratory gasses are forced through conduits 75 and 77 intochamber 127 and out of opening 123 to a gas monitor or analyzer byconnecting a vacuum system or pump to the output of the monitor asillustrated in FIG. 9.

When moisture enters sensor 113 and bridges gap 81, control circuit 165detects the conductivity change and activates solenoids 151 and 135 tooperate solenoid valves 149 and 133. Vacuum pump 53 then forces air orreference gasses through throttle valve 157, conduits 153 and 155,analyzer 27 and flow meter 31 in the direction of the arrows with"rectangle" tails. Valve 149 seals conduit 145 and prevents the flow ofair or reference gasses therethrough. During the period of solenoidoperation, the flow of air or reference gas through the analyzer enablesthe analyzer to be calibrated or adjusted to a desired reference readingsuch as "zero". Therefore, although not illustrated, an automatic"zeroing" circuit may be utilized with analyzer 27 in FIG. 9.

While solenoid 135 is operated, solenoid valve connects pressure pump107 through conduits 131 and 137 to port 121 of sensor 113. Air or apurging gas which may be connected to conduit 109, is then forced in thedirection of the arrows with "rectangle" tails through opening 125 intochamber 127 (FIG. 8) to clear the chamber of any fluid or mucousmaterial. This material is then forced through conduits 77, gap 81 andout of conduit 75 and ultimately out of the end of the patient'scatheter, thereby clearing the patient's catheter and sensor 113including gap 81 of all moisture and mucous.

Normally pressure pump 107 is connected through valve 133 to reliefvalve 141. Relief valve 141 requires a few pounds of pressure before itreleases to allow air or purging gas to flow therethrough in thedirection of the arrows with the "circle" tails. This "head" of pressureprovides a sudden surge of air or gas through sensor 113 when solenoidvalve 133 is actuated. This surge of air or gas loosens and dislodgesany moisture or mucous droplets clinging to the interior of sensor 113and the patient's catheter to enable these droplets to be dischargedfrom the catheter by the steady and continuing flow of air or gasprovided by pump 107 following the initial surge. The "head" of pressurealso provides a rapid purging response to the detection of moisture andmucous material to prevent the material from advancing into connectingport 119 in enclosure 117 before the purging flow of air or gas isestablished through the sensor. It is important that moisture and mucousnot enter connecting port 119 and contaminate the analyzer conduits.

It should be noted that vacuum pump 53 may be the vacuum system of ahospital and during normal operation it forces respiratory samples froma patient through sensor 113, flowmeter 31 and analyzer 27 in thedirection of the arrows with the "circle" tails.

It now should be apparent that the present invention provides a circuitarrangement with associated mechanical components which may be employedin conjunction with a respiratory analyzer system for purging unwantedmoisture and mucous from the system by sensing the presence of suchunwanted material to activate a purge as well as periodically purgingthe system in response to a counter.

Although particular components, etc., have been discussed in connectionwith a specific embodiment of a purging system constructed in accordancewith the teachings of the present invention, others may be utilized.Furthermore, it will be understood that although an exemplary embodimentof the present invention has been disclosed and discussed, otherapplications and electrical circuit arrangements and mechanicalconfigurations are possible and that the embodiments disclosed may besubjected to various changes, modifications and substitutions withoutnecessarily departing from the spirit of the invention.

What is claimed is:
 1. A moisture detector for sensing the presence ofmoisture in gas conduits, comprising:a pair of gas conduits fabricatedfrom electrically condutive material; a pair of electrodes, each ofwhich is electrically attached to one of said pair of gas conduits; acoupling for mounting said pair of gas conduits end-to-end, said gasconduits being separated by an interconnecting passage forming a gapbetween the adjacent ends of said pair of gas conduits and electricallyisolating said pair of electrodes from one another until a drop ofmoisture bridges said gap and electrically connects said adjacent endsof said pair of gas conduits; and means for injecting a gas into saidconduits for removing moisture from said gap and said conduits.
 2. Themoisture detector described in claim 1 wherein said coupling comprises aplastic block molded around the adjacent ends of said pair of gasconduits and the junctions of said pair of electrodes with said pair ofgas conduits to mechanically support and rigidly hold the assembly ofsaid pair of conduits and said pair of electrodes.
 3. The moisturedetector described in claim 1 wherein each of said pair of electrodeshas an opening through one end adapted to receive therein one of saidpair of gas conduits, each electrode being electrically connected to agas conduit by a spot weld between the edge of said opening and theouter surface of said gas conduit.
 4. A moisture sensor comprising:apair of electrically conductive gas conduits; an electrically insulativeinterconnecting passage for insulatively joining one end of oneelectrically conductive conduit with one end of the other electricallyconductive conduit, the ends being spaced apart within saidinterconnecting passage by a gas conducting gap so that when moisturebridges said gap, said pair of electrically conductive gas conduits areelectrically connected together; an enclosure having a chamber thereinconnected to the other end of said one of said pair of electricallyconductive gas conduits such that gas may flow between said electricallycondutive conduits and said chamber, said enclosure having a firstconnecting port therein adapted to connect said chamber to an externalgas conduit permitting gas to flow from the other end of said otherelectrically conductive conduit through said connecting port and saidchamber into said external gas conduits; and means for mechanicallyconnecting and supporting said enclosure to said electrically insulativecoupling.
 5. The moisture sensor described in claim 4 further includinga second connecting port communicating with said chamber, said secondconnecting port adapted to be connected to a source of purging gas whensaid first connecting port is connected to a gas analyzing system toremove moisture therefrom.
 6. A moisture detector for sensing thepresence of moisture in gas conduits in respiratory analysis systems,comprising:a pair of conduits for conducting respiratory gas; a couplingfor placing said pair of conduits in fluid communication; and a pair ofelectrodes mounted in said coupling, said electrodes being spaced apartand electrically isolated from another until a drop of moisture input tosaid coupling from one of said conduits forms a bridge to electricallyconnect said electrodes; and means responsive to the electricalconnection of said electrodes for injecting a gas in said conduits forremoving moisture from said conduits.
 7. A moisture sensor forrespiratory gas analysis comprising:a pair of conduits for conductingrespiratory gasses; a coupling for joining said conduits in fluidcommunication; a pair of electrodes mounted to said coupling, saidelectrodes being spaced apart and electrically isolated by an insulatinggap, said electrodes indicating the presence of moisture within saidconduits when moisture bridges said gap; and an enclosure having achamber therein connected to said gas conduits such that gas may flowbetween said conduits and said chamber, said enclosure having a firstconnecting port therein adapted to connect said chamber to an externalgas conduit to permit gas flow from said conduits and said chamber intosaid external gas conduit.
 8. The moisture sensor described in claim 7further including a second connecting port communicating with saidchamber connection to a source of purging gas when said first connectingport is connected to a gas analyzing system.